The player throws this error when the source of the player is incompatible with the license. This occurs when the domain of the source is not in the list of source domains of the license. For example, when you have yourfirstcdn.com and yoursecondcdn.com as source domains, but you use a video stream (i.e. source) from https://yourthirdcdn.com/video.m3u8, then the player will throw the above error because yourthirdcdn.com is not included in the source domains (yourfirstcdn.com and yoursecondcdn.com).
To resolve this issue you can do the following: